Research On Load Transfer Method Of Urban High-voltage Distribution Network Considering Load Forecasting

As an important intermediate link connecting the transmission network and the lower distribution network/power load,the urban high-voltage distribution network(UHVDN)plays the role of power transmission,distribution and management.With the rapid development of social economy and industrial production,the UHVDN is facing such phenomena as load fluctuation,power supply congestion and unbalanced load-distribution.Under the condition of current power constructing,load-transfer is an effective way to solve the problems above.Therefore,this paper mainly studies three aspects:load forecasting,load-transfer of UHVDN,the sequence of switching operation.Firstly,the time-distribution characteristics of load are analyzed based on the historical data,selects GDP and temperature as variable elements,and the influence of their correlation on the load is studied.The prediction method is mainly based on the two element nonlinear regression analysis method,other methods like the natural growth rate method,the gray prediction method and the quarterly trend ratio method are used to supporting.All the methods are tested by the actual calculation example.The purpose of load forecasting is to provide load data for load-transfer.Secondly,analyzed the topology of the high voltage distribution network,and the topology is described based on the link-path idea.Then,many concepts like the power supply selection factors and set of power supply paths are defined.According to the actual situation,the load-transfer model is established.Compared with the traditional method,the model in this paper reduces the dimension of the variables,and improves the linearity to a certain extent,and the better effect can be obtained by using the branch and bound method.The result of the solution is the set of switching operations.The time-sequence of switching operation is the further research of load-transfer in UHVDN,which has great influence on the reliability of power supply and the safety of system.Based on the operation principles of transfer switch,this paper collates the elements of switch operation into the form of switch operation queues.A risk assessment method is proposed,and four risk assessment functions are established to quantitatively study the impact of each switch operation on the system.A risk metric matrix similar to the distance matrix in the traditional traveling salesman problem is established.The ant colony algorithm is applied to solve the sequential problem,and corresponding adjustment is made according to the characteristics of the object.At the end of this paper,the local high voltage distribution network under the jurisdiction of a power supply company in Chongqing city of the national network is used as an example to study the problem of the design of the load transfer scheme in the "summer peak load" and the N-1 failure of the distribution network.An example is given to verify the practicability of the proposed method,which can provide reference for the actual power dispatching department.